The semiconductor nonvolatile memory has integrated memory cells, each being operative to carry out writing and reading of information in random-access basis and having an electric charge storage structure effective to memorize the information in nonvolatile state. The information is temporarily written into each memory cell in volatile state, and thereafter the temporarily written information is written at one into the respective electric charge storage structure of each memory cell, thereby effecting quick writing of nonvolatile information into the respective memory cells of multi-bits.